Machine for balancing tires



April 16, 1940.

INVENTOR.

LioYd M. Litflefield BY A TTORNEYS amass. s, 1940 UNITED STATES PATENT OFFICE I V meme. 3.3m cmc amps Lloyd M. ldttieiield, Springfield, Masa, asaignor,

bymeane en ta, to United States Bubber Company New York, N. Y., a corporation of New Jersey This invention relates to a method of balancing pneumatic tires and to a mechanism for carrying out the method. 7

Because of the relatively high speeds at which automobiles are operated it is desirable that the tire casings with which they are equipped be circumferentially balanced. In many instances otherwise perfect casings are found on inspection to be slightly out of. balance and it has heretofore been the usual practice to add weight to the light" portion of the casing by applying apatch coating of rubber'or other material to the inside of the casing to a sumcient thickness to bring the tire into substantial balance. This method is undesirable'from several viewpoints. The material applied to the casing tends to flake off when the tire is in use "and subject to constant flexing. Furthermore, it is dimcult to distribute the material properly and a material which can be so applied is relatively light inweight so that if the degree of off-balance is at all substantial an excessive amount of material has to be applied which increases the tendency to flake oil.

It is the object of my invention to overcome these dimculti'es and thereby substantially increase the possible range of adjustment, secure a v permanent balance, and at the same time secure economies in operation;

According to my invention I remove the excess of material fromthe heavy side of-the tire, rather than attempting to-add weight to the light side. Furthermore, I remove the material from the tread, which is the densest rubber element of the tire, so that a minimum of material is removed.

In theaccompanying drawing which illustrates one embodiment of my invention- Fig. 1 is a plan view of a machine for carrying out'my method; s

Fig. 2 is a side elevational view of the machine of Fig. 1;

Fig. 3 is a detail sectional view substantially on line 3-3 of Fig. 1; and

Fig. 4 is a detail sectional view substantially on line 4-4 of Fig. 2.

Referring to the drawing, the frame is shown as comprising a base portion It provided at one end with an upright ll, upon the upper end of which is mounted a cantilever member l2.

A carriage, in the form of a plate I, is slidably mounted for limited reciprocation on base It by means of bolts l5 secured to the plate and riding in slots it formed in base member ll.

Plate ll carries a pair .of spaced parallel'shafts with freely rotatable V-shaped rolls it upon which the tire casing is supported. 'Plate ll is reciprocated by means of a rack l9 secured to the under side of the plate and engaged by a pinion secured on a rock-shaft 2| journaled in bearings 22 formed in the sides of base member l0. Shaft 2| is adapted to be rocked in its bearings by means of a foot treadle 23 pivoted at one end' to the floor as at 25 and connected by an adjust able link 20 to a crank 21 secured to shaft 2|. A spring 24 connected to the'pia'te I 4 at "and to the base it at 29 tends to keep the plate in retracted position. 4

The outer end of cantilever I2 is forked as at III and a shaft 3| is journaled, as at 32, in the ends of the fork. Shaft 3| is provided outwardly of the frame with a pulley l3 inv alignment with an idle pulley 54 mounted on a stub shaft secured in base member ll. Pulleys and 34 are positioned in the plane of the tire supporting rolls l8 and carry an endless belt 31 which is provided on its outer surface with an abrasive material such as emery or the like.

Belt 31 is driven from a motor '40 mounted on base I I and provided with a pulley ll connected by belt 42 to a pulley 43 secured to a countershaft 44 mounted in spaced bearings 45 formed at the fixed end of cantilever l2. Shaft is provided with a pulley l5 connectedby. a belt 41 to a pulley 48 secured to shaft 3| intermediate bearings 22. g I

An upright 50 is mounted on base It and carries a rotatable screw 5| upon which is threaded a bracket 52 extending between the runs of belt 31. The free end of bracket 52 carries a pair of rolls 53 pivoted for angular adjustment as at 54 to the bracket. Screw 5| is adapted to be rotated to raise or lower'bracket 52 by means of a crank handle 55 secured to the upper end of the screw;

In operation a the is placed in a vertical position on rollers It, the motor 40 being in operatlon'to drive belt 31 in the direction of the arrow in Fig. 2. The operator then depresses treadle 23 to move the tread portion of the tire against the abrasive surface of the belt. The center" of overweight has been previously marked on the 50 ing amounts over a substantial arc on each side of the center of overweight. As shown in Fig. 4,

the belt flexes to conform to the surface of the tread, and by means of the adjustment of angular rolls 53, which are preferably positioned slightly above the point of tangency of the tire and belt, the pressure of the belt may be made substantially uniform across the tread.

By proper manipulation of the tire the tire is brought into balance without making any noticeable alteration in its appearance and the balanced a condition is permanent. 1

A further advantage of my machine and method is that the balancing operation can be 7 combined with the usual builin'g operation to re-- move mold marks and overflow fins from the tread, the latter being accomplished by simply giving the tire one or more complete rotations in contact with belt 31, either before or after the balancing of the-tire has been carried out.

While Ihave illustrated my invention as ap- 2,197,077 plied to the balancing of a pneumatic tire, it will the pulleys, means to drive the ibelhlatcarriage provided with spaced, freely rotatable rollers adapted to support a tire in upright position, and means to reciprocate the carriage toward and from the belt to move a tire supported thereon into and out of contact with a run of the belt at a point intermediate said pulleys, and a pair of angularly adjustable rolls mounted behind the tire engaging run of the belt to impart a predetermined; degree of transverse curvature to the V tire contacting portion of the belt. 

